The present invention relates generally to diagnostic systems for internal combustion engines, and more specifically to systems for diagnosing fault conditions associated with air handling systems including EGR components, a variable geometry turbocharger, a wastegate and/or an exhaust throttle.
When combustion occurs in an environment with excess oxygen, peak combustion temperatures increase which leads to the formation of unwanted emissions, such as oxides of nitrogen (NOx). This problem is aggravated through the use of turbocharger machinery operable to increase the mass of fresh air flow, and hence increase the concentrations of oxygen and nitrogen present in the combustion chamber when temperatures are high during or after the combustion event.
One known technique for reducing unwanted emissions such as NOx involves introducing chemically inert gases into the fresh air flow stream for subsequent combustion. By thusly reducing the oxygen concentration of the resulting charge to be combusted, the fuel burns slower and peak combustion temperatures are accordingly reduced, thereby lowering the production of NOx. In an internal combustion engine environment, such chemically inert gases are readily abundant in the form of exhaust gases, and one known method for achieving the foregoing result is through the use of a so-called Exhaust Gas Recirculation (EGR) system operable to controllably introduce (i.e., recirculate) exhaust gas from the exhaust manifold into the fresh air stream flowing to the intake manifold.
EGR operation is typically not required under all engine operating conditions, and known EGR systems accordingly include a valve, commonly referred to as an EGR valve, for controllably introducing exhaust gas to the intake manifold. Through the use of an on-board microprocessor, control of the EGR valve is typically accomplished as a function of information supplied by a number of engine operational sensors.
In addition to an EGR valve, air handling systems for modern turbocharged internal combustion engines are known to include one or more supplemental or alternate air handling control mechanisms for modifying the swallowing capacity and/or efficiency of the turbocharger. For example, the air handling system may include a wastegate disposed between an inlet and outlet of the turbocharger turbine to selectively route exhaust gas around the turbine and thereby control the swallowing capacity of the turbocharger. Alternatively or additionally, the system may include an exhaust throttle disposed in line with the exhaust conduit either upstream or downstream of the turbocharger turbine, wherein the effective flow area of the exhaust is throttle is controlled to thereby control the efficiency of the turbocharger. Finally, the turbocharger may include a variable geometry turbine, wherein the swallowing capacity of the turbocharger is controlled by controlling the geometry of the turbine.
Regardless of the number or type of air handling control mechanisms used, it is important to monitor the functionality of such mechanisms for faults or failures that may occur during operation thereof. For example, if any of the foregoing air handling control mechanisms fail due to valve sticking or similar faults, it is desirable to monitor such conditions and log appropriate faults when they occur. However, it is not desirable to monitor the operation of such air handling control mechanisms using actual air handling control mechanism sensors since some failures attributable to the air handling control mechanisms may not be distinguishable from failures attributable to the sensors themselves. What is therefore needed is a system for diagnosing fault conditions associated with air handling control mechanisms that compares the effect of the air handling control mechanisms on one or more engine operating parameters with predicted behavior thereof. Such a diagnostic system should further include the capability of distinguishing air handling control mechanism failures and fault conditions from those associated with the one or more engine operating parameter sensors.
The foregoing shortcomings of the prior art are addressed by the present invention. In accordance with one aspect of the present invention, a system for diagnosing fault conditions associated with an air handling control mechanism for an internal combustion engine comprises an air handling control mechanism responsive to a mechanism command to control fluid flow through an air handling system of an internal combustion engine, means for modeling a predicted response of an engine operating parameter as a function of the mechanism command, means for monitoring the engine operating parameter and producing an engine operating parameter signal corresponding thereto, means for computing a correlation coefficient as a function of the engine operating parameter signal and the predicted response, and means for diagnosing a fault associated with the air handling control mechanism if the correlation coefficient is below a first coefficient threshold.
In accordance with another aspect of the present invention, a system for diagnosing fault conditions associated with an air handling control mechanism for an internal combustion engine comprises an air handling control mechanism responsive to a mechanism command to control fluid flow through an air handling system of an internal combustion engine, an engine parameter sensor producing an engine operating parameter signal indicative of an operational state of an engine operating parameter, and an engine controller modeling a predicted response of the engine operating parameter as a function of the mechanism command, the engine controller computing a correlation coefficient as a function of the engine operating parameter signal and the predicted response and diagnosing a fault associated with the air handling control mechanism if the correlation coefficient is below a first coefficient threshold.
In accordance with a further aspect of the present invention, a system for diagnosing fault conditions associated with an air handling control mechanism for an internal combustion engine comprises an air handling control mechanism responsive to a mechanism command to control fluid flow through an air handling system of an internal combustion engine, a number of engine parameter sensors producing engine operating parameter signals indicative of operational states of a corresponding number of different engine operating parameters, and an engine controller modeling predicted responses of the number of engine operating parameters each as a different function of the mechanism command, the controller computing a number of correlation coefficients each as a function of one of the number of engine operating parameter signals and a corresponding one of the predicted responses, the controller diagnosing a fault associated with the air handling control mechanism if at least some of the correlation coefficients are below a first coefficient threshold.
One object of the present invention is to provide a system for diagnosing fault conditions associated with an air handling system for an internal combustion engine.
Another object of the present invention is to provide such a system for diagnosing fault conditions associated with an EGR valve, a wastegate, an exhaust throttle and/or a variable geometry turbocharger.
Yet another object of the present invention is to provide such a system for diagnosing fault conditions based on predicted responses of a number of engine operating conditions each modeled as a function of an air handling mechanism control signal.
These and other objects of the present invention will become more apparent from the following description of the preferred embodiments.